/* Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.security.authentication.encoding;

/**
 * <p>
 * Convenience base for all password encoders.
 * </p>
 *
 * @author Ben Alex
 */
public abstract class BasePasswordEncoder implements PasswordEncoder {
	// ~ Methods
	// ========================================================================================================

	/**
	 * Used by subclasses to extract the password and salt from a merged
	 * <code>String</code> created using
	 * {@link #mergePasswordAndSalt(String,Object,boolean)}.
	 * <p>
	 * The first element in the returned array is the password. The second element is the
	 * salt. The salt array element will always be present, even if no salt was found in
	 * the <code>mergedPasswordSalt</code> argument.
	 * </p>
	 *
	 * @param mergedPasswordSalt as generated by <code>mergePasswordAndSalt</code>
	 *
	 * @return an array, in which the first element is the password and the second the
	 * salt
	 *
	 * @throws IllegalArgumentException if mergedPasswordSalt is null or empty.
	 */
	protected String[] demergePasswordAndSalt(String mergedPasswordSalt) {
		if ((mergedPasswordSalt == null) || "".equals(mergedPasswordSalt)) {
			throw new IllegalArgumentException("Cannot pass a null or empty String");
		}

		String password = mergedPasswordSalt;
		String salt = "";

		int saltBegins = mergedPasswordSalt.lastIndexOf("{");

		if ((saltBegins != -1) && ((saltBegins + 1) < mergedPasswordSalt.length())) {
			salt = mergedPasswordSalt.substring(saltBegins + 1,
					mergedPasswordSalt.length() - 1);
			password = mergedPasswordSalt.substring(0, saltBegins);
		}

		return new String[] { password, salt };
	}

	/**
	 * Used by subclasses to generate a merged password and salt <code>String</code>.
	 * <P>
	 * The generated password will be in the form of <code>password{salt}</code>.
	 * </p>
	 * <p>
	 * A <code>null</code> can be passed to either method, and will be handled correctly.
	 * If the <code>salt</code> is <code>null</code> or empty, the resulting generated
	 * password will simply be the passed <code>password</code>. The <code>toString</code>
	 * method of the <code>salt</code> will be used to represent the salt.
	 * </p>
	 *
	 * @param password the password to be used (can be <code>null</code>)
	 * @param salt the salt to be used (can be <code>null</code>)
	 * @param strict ensures salt doesn't contain the delimiters
	 *
	 * @return a merged password and salt <code>String</code>
	 *
	 * @throws IllegalArgumentException if the salt contains '{' or '}' characters.
	 */
	protected String mergePasswordAndSalt(String password, Object salt, boolean strict) {
		if (password == null) {
			password = "";
		}

		if (strict && (salt != null)) {
			if ((salt.toString().lastIndexOf("{") != -1)
					|| (salt.toString().lastIndexOf("}") != -1)) {
				throw new IllegalArgumentException("Cannot use { or } in salt.toString()");
			}
		}

		if ((salt == null) || "".equals(salt)) {
			return password;
		}
		else {
			return password + "{" + salt.toString() + "}";
		}
	}
}
